Who should make the Cardinals postseason rotation, which is definitely going to eventually exist?

A month ago, arranging a pitching staff for a St. Louis Cardinals postseason run was nothing more than a framing device for an article. It certainly wasn’t based in any sort of reality–it was just a way of asking for the best four starting pitchers on the Cardinals. But a lot has chanaged in the last month–Matt Adams is a Cardinal, Tommy Pham isn’t a Cardinal, and St. Louis is home to the greatest baseball team on the planet (not hyperbole if you add a mere “over the last month” addendum to the end of it!).

Suddenly, the St. Louis Cardinals have a good chance of making the postseason. It is not literally assured, but it is plausible enough that it merits discussing. The Cardinals, of course, still have over a month before they will need to actually construct a rotation, and much can change, and the exact order used may depend on how the final few games of the season shape up (for instance, if the Cardinals find themselves in a must-win game on the final Sunday of the season, they would use their staff ace even if that meant not having him available for the first postseason game), but generally speaking, the Cardinals are probably looking at four starting pitchers who would be elevated to the role of playoff starter.

Sometimes, it is easy to determine. The 2015 Cardinals had five excellent starting pitchers throughout the season, and one of them (Carlos Martinez) missed the postseason with injury, so lining up John Lackey, Jaime Garcia, and Michael Wacha, with a fourth starter’s role as well as potential bullpen innings for Lance Lynn a logical solution. In 2018, however, while the starting rotation has been effective, it hasn’t been consistent. Some of the team’s biggest names have missed considerable playing time and/or been ineffective, while others have come seemingly out of nowhere to contend for pivotal innings.

Here is how I would arrange the Cardinals’ postseason rotation contenders as of this moment, with the line between four and five representing the literal cut-off. That said, this list is very much subject to change as new results unfold.

Miles Mikolas: Easily the rotation’s best pitcher throughout the season, the sub-3 ERA and team’s lowest FIP among starters make Mikolas the safe choice for #1 starter. There is some argument to be made that Mikolas, more of an innings-eater than most of his competition, would be better served starting Game 1 of the NLDS, I think this really only comes into play if the Cardinals can avoid the Wild Card game. For a one-game playoff, you roll with the best pitcher you have. Mikolas is the team’s best option.

Jack Flaherty: Flaherty’s impressive outing in Los Angeles last week against Walker Buehler felt like a signature moment in the early career of the Cardinals rookie. Buehler was himself an acclaimed prospect–perhaps not a capital-E Elite one, but somebody expected to be a solid top-to-mid rotation starter–and Flaherty, who was often lost in the shuffle compared to other Cardinals pitching prospects, matched and eventually exceeded him. He doesn’t throw as many innings as Mikolas, though this isn’t nearly as big of a deal in the postseason, particularly given the number of starters-by-trade that will be in the Cardinals bullpen come October.

Michael Wacha: This choice is as subject to change as any on the list–Wacha certainly has a more established record of success than Mikolas or Flaherty, but he is also currently on the Disabled List. Wacha hasn’t pitched since June 20, which is cause for concern, but he was effective (if a bit lucky, according to advanced metrics) up to that point, and while Wacha has occasionally dealt with injuries, I am willing to put some faith in the Cardinals medical staff, who seem confident that this will not negatively impact his performance.

John Gant: Remember in 2016 when the Cardinals picked up Jaime Garcia’s $12 million option for 2017 and some fans were mad about it? Well, the Cardinals almost immediately flipped Garcia for three prospects, and while two of them turned out to be nonstarters (in the “irrelevant” way, not in the “not a starter” way, though I guess both are true), one of them turned into John Gant. And Gant has been a solid starter for the Cardinals this season. His 3.56 ERA may not be spectacular, but it is even better the first and second times through the order (3.03 and 3.29, respectively, compared with 6.75 in an admittedly low number of innings the third time through the batting order), and realistically, the Cardinals shouldn’t be expecting Gant to make it more than five or six innings on a good day.

Austin Gomber: Gomber has surpassed expectations in 2018, and while I don’t see him as a long-term rotation mainstay (more of a long-term “guy you can throw into the rotation as the fifth starter and not hate it”), the results are hard to argue against. His last start, at Coors Field against the Colorado Rockies, was downright impressive, going six and striking out a batter per inning. I think Gant and Gomber are essentially a coinflip at this point–if you prefer Gomber, I disagree, but this isn’t the hill (or mound, if you prefer bad puns) I’m going to die on.

Carlos Martinez: Martinez has looked more or less like his normal self coming out of the bullpen since returning from the Disabled List–he walked two in his first three innings, but, like, if you just remove one of those two, it wouldn’t look that concerning on a rate basis. But, in addition to the “if it ain’t broke don’t fix it” principle is Martinez’s health–he is returning from his third instance of missing starters on the season (his second trip to the Disabled List) and while he will, certainly among current Cardinals pitchers, by the team’s de facto ace entering 2019, it might be best in the long term to proceed with caution and allow him to be used as a weapon out of the bullpen.

Adam Wainwright: He’s looked good in rehab starts and deep down, once you get past my sabermetric facade, I’m a sentimental old fool. That said, I’m also terrified of Mike Shildt falling in love with Wainwright far more than I am certain than Wainwright is ready to become something resembling Vintage Wainwright. If Mike Matheny were still managing, Wainwright would rank lower, but I have just enough faith in Shildt to keep him ahead of some guys.

Luke Weaver: He got off to a good enough start to his season in the rotation, but his decline throughout the season makes me worried about his potential for the remainder of the season. He has too much talent to abandon all hopes of him contributing whatsoever, but for now, I’m keeping him in the bullpen.

Daniel Poncedeleon: His debut as a starter was spectacular, but there’s a reason the team has avoided giving him more than two total starts (though he is expected to make start #3 on Saturday). His sheer lack of MLB inning volume makes any statistical argument based on far too small of samples, but the lack of trust in him seemingly suggests a lack of faith. Maybe he makes it as a reliever.

Tyson Ross: He’s looked good so far, but the fact that I keep forgetting he’s on the team makes me think the Cardinals claimed him off waivers from the San Diego Padres solely as roster depth. Which is fine! But I’m not exactly ready to give him the keys to the championship drive. Also, if anyone cites the Cardinals owing him a bonus for every start he makes as an argument against him making postseason starts for the Cardinals, I’m calling the cops on you.